1. Field of the Invention
This invention relates to a method for producing wax esters biosynthetically. More particularly, this invention relates to a method for producing wax esters using highly branched alkanes as a starting material and a novel genus of soil bacteria, which appears to be closely related to Acinetobacter. The bacteria, designated as MVAB Hex1 (ATCC Accession Number PTA-4839) (ATCC, P.O. Box 1549, Manassas. Va. 20108), is exemplary of a suitable microorganism for producing wax esters in accordance with the method of this invention.
2. Description of Related Art
Wax esters are used in numerous industrial and commercial products, including cosmetics, candles and other wax-based products, inks, lubricants, and coatings. For example, long chain wax esters have been employed as a lubricant for providing mold release for molded products such as steel casting and for preventing destructive metal-to-metal contact under high temperature and/or pressure conditions, such as occur in a variety of industrial machines. Historically, the primary sources for such wax esters were natural sources such as the sperm whale and the jojoba plant. In recent years, certain microorganisms have been found to be suitable sources of wax esters. Through metabolic action, wax esters can be produced from inexpensive, readily available hydrocarbons. U.S. Pat. No. 3,409,506 to Stevens et al. teaches the biosynthesis of wax esters by aerobically subjecting aliphatic hydrocarbons to the metabolic action of a gram negative bacteria, Micrococcus cerificans (also referred to as Acinetobacter sp. HO1-N), in the presence of an aqueous mineral salts solution containing a limited concentration of mineral nutrients such as magnesium, calcium and combinations thereof. U.S. Pat. No. 4,404,283 to Neidleman et al. teaches a method for producing wax esters containing either 0,1 or 2 internally located carbon-carbon double bonds from saturated hydrocarbons, with no more than 1 carbon-carbon double bond being in fatty acid or the fatty alcohol segments by the metabolic action of microorganisms including Mycobacterium ceriformans, Mycobacterium fortuitum, Mycobacterium rhodocrous, Candida lipolytica, Candida guilliermondii, Nocardia brasiliensis, Hormondendrum hordei, Rhizopus arrhizus, Fusarium lini, Corynebacterium paurometabolum, Corynebacterium diptheriae and Micrococcus cerificans. Suitable starting materials are indicated to be C15 through C30 n-alkanes, n-alcohols and n-acids and petroleum hydrocarbon fractions in the C15 through C30 range. And, U.S. Pat. No. 4,567,144 to Neidleman et al. teaches a process for producing wax esters which includes aerobically incubating a culture of microorganisms of the genus Acinetbacter species HO1-N in an aqueous mineral salts solution containing ethanol as a primary food source.
It is axiomatic that the characteristics of products produced from wax esters are determined at least in part by the starting materials used to produce the wax esters. One characteristic of wax esters produced by known microbial systems is that the principal wax esters have a carbon chain length in the fatty acid and fatty alcohol segments equal to the chain length of the hydrocarbon used as the feedstock. Thus, the chain lengths of the fatty acid and fatty alcohol in the wax esters can be controlled by the chain length of the feedstock used. Likewise, microbial production of wax esters from aliphatic hydrocarbon chain feedstocks typically produces wax esters that are saturated rather than unsaturated. Such wax esters are not suitable for use as lubricant additives, which typically require that the wax esters have carbon chain lengths of at least 14 carbons in both the fatty acid and fatty alcohol segments and the presence of an internal carbon-carbon double bond in one or both segments. It will, thus, be apparent to those skilled in the art that the production of wax esters from more complex hydrocarbon feedstocks, such as highly branched alkane hydrocarbons, may result in a wider, more complex range of wax esters, which, in turn, provides the potential for improving existing products made from wax esters as well as the potential for developing new products.
Although chemical synthesis of wax esters is possible, microbial production of wax esters is preferable to chemical means of synthesis because it affords better control over the composition of the final product. The present invention deals with microbial processes for the production of wax esters, specifically using highly branched alkane hydrocarbons as a starting material.